Hydrazodicarboxylates and use thereof as blowing agents

ABSTRACT

Certain hydrazodicarboxylates, namely polymers or oligomers made by reacting hydrazine with polyfunctional haloformates, especially difunctional haloformates, cyclized forms of said oligomers and condensation products of hydrocarbyl carbazates with polyfunctional, especially difunctional, haloformates are useful as chemical blowing agents for expanding gas-expandable polymeric materials. These compounds are novel.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional application of copending applicationSer. No. 456,994 filed Apr. 1, 1974, now U.S. Pat. No. 3,894,974, issuedJuly 15, 1975, which is a continuation-in-part of application Ser. No.354,818 filed Apr. 26, 1973, now abandoned.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to the production of gasexpanded polymericmaterials with a new class of chemical blowing agents, namely certainhydrazodicarboxylates. These compounds are novel.

2. Description of the Prior Art

Blowing agents which decompose at relatively high temperatures are notnew. U.S. Pat. No. 3,235,519 discloses using sulfonyl semicarbazides asblowing agents for polymeric materials which soften above 170°C. Theseblowing agents are particularly suitable for expanding high densitypolyethylenes, and many other rubbery and plastic polymers.

U.S. Pat. NO. 3,554,397 discloses the use of certain dihydrocarbyl,especially dimethyl and diethyl, hdyrazodicarboxylates, as blowingagents in polyamide type polymers. However, this patent does not suggestthe particular hydrazodicarboxylates of the present invention or theunexpected advantages thereof which are discussed below.

SUMMARY OF THE INVENTION

This invention provides a new class of blowing agents which begin todecompose non-explosively, and controllably, at temperatures not lowerthan 200°C, and preferably not lower than 225°C, but have high heatstability at temperatures below 200°C. Thus, they are useful forexpanding polymeric materials that soften at, or below, these hightemperatures. These new compounds are particularly suitable as hightemperature blowing agents because of their especially low rate ofsublimation even at elevated temperatures.

Broadly, the new class of blowing agents of the present inventionincludes certain hydrazodicarboxylates namely polymers or oligomers madeby reacting hydrazine which polyfunctional haloformates, cyclized formsof such oligomers, and certain condensation products ofhydrocarbylcarbazates with polyfunctional haloformates. Upondecomposition, these blowing agents produce olefins, carbon dioxide,carbon monoxide, and alcohols, and smaller amounts of nitrogen.

The method of the present invention comprises incorporating in agas-expandable polymeric material at least one blowing agent which is anoligomer, cyclized form thereof, or a condensation product of the typesfully disclosed below, and then heating the resultant composition to atemperature above the decomposition temperature of the blowing agent tocause it to liberate gas and thereby expand the polymeric material. Thetechniques employed to effect the expansion and formation of the finalexpanded product will be obvious to workers of ordinary skill in the artfrom the following disclosure.

The term "polymeric material" as used herein means homopolymers,interpolymers, graft polymers, and mixtures and blends of two or more ofthese, and includes thermoplastic, thermosetting and rubbery polymers.In particular, the new blowing agents of the invention are useful forexpanding polymers that have high processing temperatures such as thepolycarbonates, phenylene oxidebased resins, poly(arylsulfones), thevarious nylons, polyesters, certain polystyrenes, polypropylene, poly(styrene-acrylonitrile), polyacetals, urethane elastomers, polyvinylpolymers, poly(phenylene sulfide), poly(methylpentene), certainpolyethylenes, polyimides, poly(aryl ethers), ABS polymers,polyacrylics, cellulosic polymers, halogenated polymers, especially thefluoroplastics, poly(ethylene-vinyl acetate), and polymer alloys.

Generally, the amount of blowing agent used will depend on the nature ofthe polymeric material to be expanded, and the desired density of thefoam to be produced. Usually, 0.05 to 15, and, most often, 0.1 to 5.0parts blowing agent are employed, based on 100 parts of polymericmaterial by weight. The blowing agents can be used alone, or incombination with other blowing agents. Activating substances can be usedto increase the gasreleasing efficiency, or to lower the normaldecomposition temperature, of the blowing agents of the invention. Otheradditives such as plasticizers, fillers, nucleating agents, and thelike, can also be added to the polymer to be expanded.

The addition polymers or oligomers of the present invention are made byreacting hydrazine with polyfunctional haloformates, and preferably byreacting hydrazine with difunctional haloformates, especiallychloroformates, and have the formula (I); ##EQU1## where n is a numberin the range 1 to 100, preferably 2 to 50, X is chlorine, bromine oriodine, and A is a divalent radical selected from the group consistingof alkylene radicals having 2 to 6 carbon atoms, arylene radicals having6 to 12 carbon atoms, oxydialkylene radicals having 4 to 12 carbonatoms, oxydiarylene radicals containing 12 to 20 carbon atoms,alkylenediphenylene radicals in which the alkylene group has from 1 to 6carbon atoms, and alkylidenediphenylene radicals in which the alkylidenegroup has from 1 to 6 carbon atoms. Examples of these radicals are:methylene, ethylene, propylene, isopropylene, butylene, isobutylene,pentamethylene, hexamethylene, phenylene, tolylene, naphthylene,biphenylene, oxydiethylene, oxydipropylene, oxydibutylene,oxydipentamethylene, oxydihexamethylene, oxydiphenylene, oxyditolylene,oxydinaphthylene, methylenediphenylene, ethylenediphenylene,propylenediphenylene, ethylidenediphenylene, n-propylidenediphenylene,and isopropylidenediphenylene. If cyclization of these oligomers occurs,the terminal hydrogen and halogen radicals will not be present. Thecyclized forms of these oligomers are equally useful as blowing agents.

The second group of blowing agents of the invention are the condensationproducts of hydrocarbyl carbazates with polyfunctional haloformates, andpreferably with difunctional chloroformates. These compounds have theformula (II): ##EQU2## where A has the meaning given above in referenceto formula (I), R and R' are the same or different, but preferably thesame, and are hydrocarbyl groups such as primary, secondary or tertiarybranched-chain and straightchain alkyl radicals having 1 to 8 carbonatoms; cycloalkyl radicals containing 5 to 8 carbon atoms, especiallycyclohexyl; and aryl groups having 6 to 10 carbon atoms and aralkyl andalkaryl radicals containing 7 to 10 carbon atoms, such as phenyl,benzyl, the tolyls and the xylyls.

Among these compounds are the reaction products of ethyleneglycolbis(chloroformate) or diethylene glycolbis(chloroformate) with analkyl carbazate such as methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec. butyl or tert. butyl carbazate.

The compounds of formula (II) can be made by reacting a difunctionalhaloformate with a hydrocarbylcarbazate. Schematically, this process isrepresented as follows: ##EQU3##

In practice, this process is carried out at temperatures of 20° to100°C, and atmospheric pressure, in alcoholic or aqueous media, and inthe presence of an acid sequestering agent such as an alkali metalcarbonate. Compounds of formula (II) include those listed below, suchasethylenebis(-methyl hydrazodicarboxylate)*ethylenebis(-ethylhydrazodicarboxylate)ethylenebis(-n-propylhydrazodicarboxylate)ethylenebis(-isopropylhydrazodicarboxylate)ethylenebis(-n-butylhydrazodicarboxylate)ethylenebis(-isobutylhydrazodicarboxylate)ethylenebis(-sec-butylhydrazodicarboxylate)ethylenebis(-tert-butylhydrazodicarboxylate)ethylenebis(-amylhydrazodicarboxylate)ethylenebis(-isoamylhydrazodicarboxylate)ethylenebis(-hexylhydrazodicarboxylate)ethylenebis(-heptylhydrazodicarboxylate)ethylenebis(-octylhydrazodicarboxylate)ethylenebis(-cyclopentylhydrazodicarboxylate)ethylenebis(-cyclohexylhydrazodicarboxylate)ethylenebis(-phenylhydrazodicarboxylate)ethylenebis(-tolylhydrazodicarboxylate)ethylenebis(-benzyl hydrazodicarboxylate) *also maybe named ethylenebis(3-carbomethoxy carbazate)

    and                                                                           oxydiethylenebis(methyl hydrazodicarboxylate)                                 oxydiethylenebis(ethyl hydrazodicarboxylate)                                  oxydiethylenebis(n-propyl hydrazodicarboxylate)                               oxydiethylenebis(iospropyl hydrazodicarboxylate)                              oxydiethylenebis(n-butyl hydrazodicarboxylate)                                oxydiethylenebis(isobutyl hydrazodicarboxylate)                               oxydiethylenebis(sec-butyl hydrazodicarboxylate)                              oxydiethylenebis(tert-butyl hydrazodicarboxylate)                             oxydiethylenebis(amyl hydrazodicarboxylate)                                   oxydiethylenebis(isoamyl hydrazodicarboxylate)                                oxydiethylenebis(hexyl hydrazodicarboxylate)                                  oxydiethylenebis(heptyl hydrazodicarboxylate)                                 oxydiethylenebis(octyl hydrazodicarboxylate)                                  oxydiethylenebis(cyclopentyl hydrazodicarboxylate)                            oxydiethylenebis(cyclohexyl hydrazodicarboxylate)                             oxydiethylenebis(phenyl hydrazodicarboxylate)                                 oxydiethylenebis(tolyl hydrazodicarboxylate)                                  oxydiethylenebis(benzyl hydrazodicarboxylate)                                 Also                                                                          isopropylidenebis(3-carbomethoxy phenylcarbazate)**                           isopropylidenebis(3-carbethoxy phenylcarbazate)                               isopropylidenebis(3-carbo-n-propoxy phenylcarbazate)                          isopropylidenebis(3-carbisopropoxy phenylcarbazate)                           isopropylidenebis(3-carbo-n-butoxy phenylcarbazate)                           isopropylidenebis(3-carbisobutoxy phenylcarbazate)                            isopropylidenebis(3-carbo-sec-butoxy phenylcarbazate)                         isopropylidenebis(3-carbo-tert-butoxy phenylcarbazate)                        isopropylidenebis(3-carbamyloxy phenylcarbazate)                              isopropylidenebis(3-carboisoamyloxy phenylcarbazate)                          isopropylidenebis(3-carbohexyloxy phenylcarbazate)                            isopropylidenebis(3-carboheptyloxy phenylcarbazate)                           isopropylidenebis(3-carboctyloxy phenylcarbazate)                             isopropylidenebis(3-carbocyclopentyloxy phenylcarbazate)                      isopropylidenebis(3-carbocyclohexyloxy phenylcarbazate)                       isopropylidenebis(3-carbophenoxy phenylcarbazate)                             isopropylidenebis(3-carbotoloxy phenylcarbazate)                              isopropylidenebis(3-carbobenzoxy phenylcarbazate)                              **May also be named isopropylidendiphenylenebis (methyl                       hydrazodicarboxylate)                                                    

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The following examples illustrate the preparation of some of thehydrazodicarboxylate addition polymers and condensation products of theinvention, and their use as blowing agents for producing expandedpolymeric material.

EXAMPLE I Reaction of Ethylenebis(Chloroformate) with Ethyl Carbazate

A 1-liter flask was charged with 104 g (1.0 mole) of ethyl carbazate, 53g (0.5 mole) of sodium carbonate, and 250 ml of water. To this mixturewas added 93.5 g (0.5 mole) of ethylenebis(chloroformate) over a periodof 45 minutes, while agitating, during which the temperature rose to65°C. The mixture was then heated to reflux for one hour. The oily layerwas separated, poured into hexane, and a product crystallized. Theproduct was filtered, washed with hexane and with hot benzene, and theremaining crystalline solid weighed 109 grams and melted at 132°C. Theproduct began to decompose at 227°C. Dumas analysis gave 16.84%nitrogen; the calculated value is 17.39%. The product has the followingstructural formula: ##EQU4##

EXAMPLE II Reaction of Ethylenebis(Chloroformate) with Methyl Carbazate

A 1-liter flask was charged with 90 g (1.0 mole) of methyl carbazate, 53g (0.5 mole) sodium carbonate and 250 ml ethanol. The temperature wasadjusted to 60°C., and 93.5% g (0.5 mole) of ethylene bis(chloroformate) was added dropwise over a period of one-half hour as thetemperature rose to 75°C. After addition was complete, the mixture wasrefluxed one-half hour, sodium chloride crystals were filtered off, andthe ethanol filtrate evaporated to one-half its volume. Upon standingovernight, a product crystallized, was filtered, washed with hexane anddried. The product weighed 130 g, melted at 122°-126°C, and decomposedin the range 250°-300°C. Dumas analysis gave 18.57% nitrogen; thecalculated value is 19.05%. The product has this structural formula:##EQU5##

EXAMPLE III Preparation of Addition Product of Ethylenebis(Chloroformate) with Hydrazine

A 2-liter reaction flask was charged with 106 g (1. mole) of sodiumcarbonate, 33 g (1.0 mole) of anhydrous hydrazine, and 750 ml water. Tothis stirred mixture, 187 g (1.0 mole) of ethylenebis(chloroformate) wasadded dropwise over a period of 1.5 hours while the reaction temperaturewas held below 50°C. After stirring overnight, a white solid formed, wasfiltered, washed well with water, and dried at 60°C. The yield was 116g, or 80% of theory. The product melted at 166°-183°C., and decomposedto produce blowing gas in the range 240° to 290°C. Upon completedecomposition, this product yielded 169 cc of gas per gram.

Analysis of the compound gave these data: percent nitrogen calculated,19.18, found 18.33; percent carbon calculated, 32.87, found 31.55; andpercent hydrogen calculated, 4.10, found 4.31.

EXAMPLE IV Preparation of Ethylenebis(n-propyl hydrazodicarboxylate)

A 3 liter flask was charged with:

500 ml ethanol

260 g (2.2 mole) n-propyl carbazate

176 g (2.1 mole) sodium bicarbonate

The mixture was stirred as 187 g (1.0 mole) ofethylenebis(chloroformate) was dropped in over 45 minutes. Thetemperature increased as the chloroformate was added and a water bathwas applied to keep the temperature under 40°C. Carbon dioxide wasevolved in a rapid stream during the reaction. Finally, the mix wasstirred an additional hour and a liter of cold water was graduallyadded. The diluted mix was stirred and cooled for an additional 2 hours,whereupon the product separated as a white crystalline solid. This wasfiltered off, washed with water and dried.

Yield = 245g; mp 107°-108°C

EXAMPLE V

Preparation of Oxydiethylenebis(methyl hydrazodicarboxylate)

A 2-liter flask charged with:

53g sodium carbonate

250 ml ethanol

99g (1.1 mole) methyl carbazate

Mix was stirred as 115.5g (0.5 mole) of oxydiethylenebis(chloroformate)was added dropwise over 1/2 hour, holding the reaction temperature under50°C. Following the addition the mixture was stirred and warmed to 70°C.for 1 hour. The separated sodium chloride was filtered off (60g) andethanol was evaporated from the filtrate. The oily residue wascrystallized in hexane.

Yield = 175g; mp 100°-125°C

This product was recrystallized in benzene

    Analysis       Calculated    Found                                            ______________________________________                                        %C             35.50         34.87                                            H              5.32          5.49                                             N              16.97         16.68                                            ______________________________________                                    

EXAMPLE VI Preparation of Oxydiethylenebis (ethyl hydrazodicarboxylate)

Into a 2-liter three -neck flask was charged

53 grams (0.5 mole) sodium carbonate

250 ml ethanol

114.5 (1.1 mole) ethylcarbazate

The mixture was stirred as 115.5g (0.5 mole) ofoxydiethylenebis(chloroformate) was added dropwise over one-half hour,holding the temperature under 50°C. After the addition was complete themix was warmed to 70°C for 1 hour. The separated sodium chloride wasfiltered off and then ethanol was evaporated from the filtrate. The oilyresidue was crystallized from benzene.

Yield = 187g; mp. 116°-122°C.Analysis: CalculatedFound______________________________________%C 39.34 39.47H 6.01 6.04N15.30 15.28______________________________________

EXAMPLE VII Preparation of Oxydiethylenebis(isopropylhydrazodicarboxylate)

A 2-liter flask was charged with:

53 grams (0.5 mole) sodium carbonate

250 ml ethanol

130 g (1.1 mole) isopropyl carbazate

The mixture was stirred as 115.5g (0.5 mole) ofoxydiethylenebis(chloroformate) was added over one-half hour, holdingthe reaction temperature under 50°C. After addition was complete the mixwas heated to 70°C. and allowed to stir for 1 hour. The sodium chlorideprecipitate was filtered off (63g). The ethanol was evaporated from thefiltrate and the oily residue was crystallized from a 50/50 mix ofbenzene and hexane.

Yield = 173g; mp 101°-104°C

This material decomposes to produce gaseous products at205°-270°C.Analysis CalculatedFound______________________________________%C 42.64 42.66H 6.60 6.80N14.27 14.22______________________________________

EXAMPLE VIII Preparation of 4,4'-Isopropylidenebis(N'-carbisobutoxyphenyl carbazate)

Into a 2-liter flask was introduced:

500 ml ethanol

145.7 g (1.1 mole) isobutyl carbazate

84 g (1.0 mole) sodium bicarbonate

The mixture was stirred as 176.5g (0.5 mole) of bisphenol Abischloroformate was added over 1/2 hour, holding the temperature under50°C. Then the mixture was stirred for 1/2 hour as the temperature wasincreased to 70°C. The separated sodium chloride was filtered off (60 g)and the ethanol was removed from the filtrate (topped to 150°C. 12mm).The clear yellow oil was poured from the flask and allowed to cool andharden.

Yield = 28.2g light yellow resin; mp = 65°-70°C; dec 210°-300°C.

EXAMPLE IX Expansion of Polysulfone Resin with Ethylene bis (ethylhydrazodicarboxylate)

Ethylenebis(ethyl hydrazodicarboxylate) was tumble-blended with pelletsof polysulfone resin, coded P-1700, and made by Union Carbide Company.These pellets were fed into an extruder (Laboratory Plastic Extruder,Table Model, made by Wayne Machine & Dye Co., and having a 0.75 inchdiameter, and a length/diameter ratio of 20:1), under the conditionsshown in Table I. The density measurement of the expanded extrudatedemonstrates that the blowing agent of the invention expands thepolysulfone effectively, and lowers its density significantly.

                                      TABLE I                                     __________________________________________________________________________    Expansion of Polysulfone with Ethylenebis(ethyl hydrazodicarboxylate)                      %Blowing  Extruder Temperature °C                                                                Screw     %Density                     Blowing Agent                                                                              Agent by Weight                                                                         Rear                                                                              Front                                                                             Die Stock                                                                             Speed                                                                             Density                                                                             Reduction                    __________________________________________________________________________    None (Resin alone)                                                                         --        --  --  --  --  --  1.22265                                                                             --                           Ethylenebis(ethyl hydra-                                                                   1.0       277 299 243 263 30  0.44370                                                                             63.4                          zodicarboxylate)                                                             __________________________________________________________________________

EXAMPLE X Expansion of Polycarbonate Polymer

A 5% glass-filled polycarbonate polymer (Lexan "FL 900." product ofGeneral Electric Company) was injection molded, using 1 part of theblowing agents listed below per one hundred parts of resin, employing a41/2 oz. Battenfeld reciprocating screw injection molding machine.

                  Table                                                           ______________________________________                                        Blowing Agent                                                                            Sample Weight (g)                                                                            % Weight Reduction                                  ______________________________________                                        None       150            --                                                  EEHD       93             38                                                  EIPHD      90             40                                                  EIBHD      90             40                                                  OIPHD      74             51                                                  ______________________________________                                         EEHD = ethylenebis(ethyl hydrazodicarboxylate)                                EIPHD = ethylenebis(isopropyl hydrazodicarboxylate)                           EIBHD = ethylenebis(isobutyl hydrazodicarboxylate)                            OIPHD = oxydiethylenebis(isopropyl hydrazodicarboxylate)                 

The above results indicate the efficiency of the compounds of theinvention in effectively expanding a thermoplastic resin.

The new blowing agents of the present invention have an unexpectedadvantage over simple dihydrocarbyl hydrazodicarboxylates in that theagents of the invention undergo less sublimation or heat loss whenheated to elevated temperatures. This is demonstrated by the data in thefollowing table.

    ______________________________________                                        Heat Loss(% by weight) of Blowing Agents                                                     Exposure Time at 250°F                                  Compound          1 hr.  2 hrs.  3 hrs.                                                                              4 hrs.                                 ______________________________________                                        Diethyl hydrazodicarboxylate                                                                     8.3   39.5    53.3  99.5                                   Di-n-propyl hydrazodicarboxylate                                                                 9.0   24.3    31.7  98.9                                   Diisopropyl hydrazodicarboxylate                                                                23.6   48.0    62.5  99.9                                   Diisobutyl hydrazodicarboxylate                                                                  9.6   16.9    30.3  99.4                                   Ethylenebis                                                                   (2-carbethoxy carbazate)                                                                         0.3   0.3     0.6   8.1                                    ______________________________________                                    

Heat loss measurements on homologues of ethylenebis (2-carbethoxycarbazate) such as the 2-carbomethoxy carbazate, the 2-carbisopropoxycarbazate and the 2-carbisobutoxy carbazate gave very similar results.

The heat loss test used was the standard one known to the art formeasuring the degree of sublimation or heat loss of chemical andpolymeric materials. The temperature in the air oven used was250°F(ca.121°C).

The lower degree of sublimation or heat loss of the blowing agents ofthe invention is advantageous because it indicates a significantly lowerloss of blowing agents of the invention during the step of drying thepolymer-blowing agent mixture which commonly precedes the shaping orother processing operation.

What is claimed is:
 1. An oligomer of the formula ##EQU6## wherein n isa number in the range of from 1 to 100, X is chlorine, and A is adivalent radical selected from the group consisting of alkylene radicalshaving 2 to 6 carbon atoms, arylene radicals 6 to 12 carbon atoms,oxydialkylene radicals having 4 to 12 carbon atoms, and oxydiaryleneradicals containing 12 to 20 carbon atoms, alkylenediphenylene radicalsin which the alkylene group has from 1 to 6 carbon atoms, andalkylidenediphenylene radicals in which the alkylidene group has from 1to 6 carbon atoms.
 2. The oligomer of claim 1, wherein A is selectedfrom the group consisting of methylene, ethylene, propylene,isopropylene, butylene, isobutylene, pentamethylene, hexamethylene,phenylene, tolylene, naphthylene, biphenylene, oxydiethylene,oxydipropylene, oxydibutylene, oxydipentamethylene, oxydihexamethylene,oxydiphenylene, oxyditolylene, oxydinaphthylene, methylenediphenylene,ethylenediphenylene, propylenediphenylene, ethylidenediphenylene,n-propylidenediphenylene, and isopropylidenediphenylene.
 3. The oligomerof claim 2, wherein A is ethylene.